A metallic shell plating of a predetermined shape for the marine vessel is manufactured by developing the shell plating on a metallic flat plate and bending the flat plate in the predetermined shape. To accurately machine the flat plate into the shell plating of predetermined shape, it is required that the shell plating is appropriately developed on the flat plate.
Conventionally, the shell plating developing methods typically include a geodesic line developing method, a diagonal line developing method, an orthogonal forward method, and an orthogonal return method. With the geodesic line developing method, a plurality of planes (frame planes) x in which the shell plating is cut crosswise and a plurality of intersecting lines (frame lines) y between the frame planes x and the shell plating curved face are determined, as shown in FIG. 12. Also, a plane-of-sight z intersecting (typically orthogonal to) the frame planes x is determined, and an intersecting line (line-of-sight) v between the plane-of-sight z and the shell plating curved face is determined. Moreover, a line on the shell plating curved face connecting both ends of the line-of-sight v in the shortest distance is determined as a geodesic line w. And the geodesic line w is developed as a straight line with the actual length on the flat plate, and the shell plating is developed on the flat plate with reference to this straight line.
When the developed flat plate is machined into the shell plating in which the lateral bending is severer than the longitudinal bending, the lateral bending is firstly made under a condition in which the amount of extension or shrinkage within the face is relatively small, and the longitudinal bending is made by drawing. In this case, the plate is shrunk by increasing the plate thickness, but it is required to have a larger size before machining corresponding to the shrinkage ratio. At this time, in developing the shell plating on the flat plate, the curved shell plating is extended to increase the area, and an increased area by extension is shrunk in machining to form the longitudinal bending.
However, according to a knowledge of the inventor of this application, it is difficult to say that the machining of the shell plating from the flat plate developed by the geodesic line developing method is suitable for the shell plating especially in a bow and stern portion with large curvature. That is, it cannot be said that the shell plating is optimally developed to the flat plate, and the amount of machining the developing flat plate into the shell plating becomes unnecessarily large, so that the machining efficiency is not always excellent. This is because the conventional developing method greatly depends on the knowledge and experience.
Thus, an object of the invention is to provide a shell plating developing method, a shell plating manufacturing method, and a computer program associated with the methods that leads to reduction of the amount of machining and improvement of the efficiency in manufacturing the shell plating.